Tridentate Chelation Coordinated Bismuth Halide Perovskite for High-Performance X-ray Detection

A3B2X9 (329-type) low-dimensional lead-free bismuth halides are emerging as promising candidates for next-generation X-ray detectors, yet their application is limited by intrinsic structural disorder and insufficient crystallinity. Herein, we develop a multidentate chelation strategy using nitrilotriacetic acid (NTA) to modulate the crystallization kinetics and defect chemistry of zero-dimensional (0D) MA3Bi2I9 perovskite films. The strong tridentate coordination and steric hindrance of NTA effectively retard rapid crystal growth, suppress grain agglomeration, and passivate interfacial Bi vacancy defects; as a result, the optimized NTA-modified MA3Bi2I9 films achieve a low trap density and improved mobility-lifetime product. The resultant X-ray detector exhibits an ultrahigh sensitivity of 9892.7 μC Gyair-1 cm-2, an ultralow detection limit of 12.6 nGyair s-1, and superior operational stability. This work provides a facile strategy for high-performance, stable lead-free X-ray detection devices toward low-dose imaging applications.